Generally, a conventional bicycle pedal, as disclosed in Japanese Utility Model Laid-Open Gazette No. Sho 57-46,092, includes a pedal shaft comprising a base mounted on the crank shaft, an intermediate shaft portion extending axially outwardly from the base and an utmost end portion. The pedal is provided with a first ball bearing between the base and the intermediate shaft portion in proximity to the crank arm, and a second ball bearing between the utmost end portion and the axially outside portion of the pedal body, the pedal body being supported rotatably to the pedal shaft.
The pedal shaft is supported to the crank arm in cantilever fashion and the base is subjected to the maximum bending moment. As a result, the base must be thick in order to withstand the maximum bending moment, in other words, the maximum treading force.
The treading force acting on the pedal body, depending upon the cyclist's pedaling posture, is transmitted for the most part (about 75%) through the second ball bearing to the pedal shaft from the outside portion of the pedal body spaced apart from the crank arm. Accordingly, it is required to make the diameter of the utmost end portion at the pedal shaft large enough to bear the treading force the same as that of the base.
Therefore, the thickness of the pedal body between its upper foot bearing surface and its lower foot bearing surface is restricted by the diameter of the pedal shaft, thereby creating a problem in that it is difficult to make the thickness thereof smaller than a predetermined value.
In other words, the thickness of the pedal body depends upon the diameter of the base subjected to the maximum bending moment and the size of the ball bearing at the base side, and cannot be reduced. Hence, the road clearance between the pedal and the ground cannot be increased with the result that the angle of inclination of the bicycle relative to the ground cannot be large.
When the conventional pedal is intended to ensure a large road clearance, the foot bearing at the axially inside portion of the pedal body adjacent to the first ball bearing is sacrificed and other portions are made smaller in thickness that the axially inside portion, thereby enabling the road clearance to be increased. On the other hand, the foot bearing surface at the crank arm side is ineffective and the treading force for actual use moves away from the crank arm to an extent of the length of the axially inside portion larger in thickness, thereby creating a problem in that the cyclist's posture becomes improper with the result that the transmission efficiency of the treading force is decreased. Hence, it is impossible to fundamentally solve the above problems.